Darryl wrote:
> >
> Could somebody elabourate for those of us not in the US? We cannot get a
> password.
>
> Darryl <dinoguy@interlog.com
Here's the article from NY Times Cybertimes:
Did Dinosaurs Break the Sound Barrier?
By JOHN NOBLE WILFORD
Move over, Chuck Yeager, and give way to supersonic
dinosaurs. At least 150 million years before Yeager in 1947 became the first
human to break the sound barrier in a rocket plane, the largest dinosaurs, a
group known as sauropods, could have mustered the right stuff to send sonic
booms resounding over the Mesozoic landscape. No, the 100-ton creatures never
got off the ground. All they would have had to do was flick their long tails
like a bullwhip.
The idea had occurred to some paleontologists examining fossils
of
the enormous sauropod tails, which tapered to thin tips. Could
they
have been used like whips to defend themselves or to produce a
loud "crack" to intimidate predators or communicate with fellow
sauropods, including potential mates? As physicists have known
since 1958, the crack of a whip is actually the shock wave, or
sonic boom, caused by the thin tip of a whip exceeding the speed
of sound for one moment.
No one had put the idea to a test until a master of computer
simulations, Dr. Nathan P. Myhrvold, of the Microsoft Corp.,
struck
up an extended electronic-mail conversation with a leading
dinosaur expert, Dr. Philip J. Currie, of the Royal Tyrrell
Museum of
Paleontology, in Drumheller, Alberta. The result could be the
beginning of a new research specialty that Myhrvold calls
cyberpaleontology.
In analyzing fossils and developing computer models of sauropod
tails, the two researchers said they had found evidence that
dinosaurs like Apatosaurus (also known as Brontosaurus) and
Diplodocus could indeed have flicked their tails to supersonic
velocities. But the sonic booms produced by the 3,500-pound tails
of these behemoths would probably have sounded more like cannon
fire than the
crack of a bullwhip.
Myhrvold and Currie described the research in interviews and in a
report in this month's issue of the journal Paleobiology. They conducted a
variety of computer simulations, testing different assumptions about the
biomechanical capabilities of these giant dinosaurs. They compared tails with
whips in their computer analysis to see how similarly they behaved.
"In all cases, it was easy to find simulations that produced
supersonic motion," the scientists wrote. "The
geometric scaling of vertebral dimensions found in the various
diplodocids strongly suggests that any of them, or
non-diplodocid sauropods with 'whiplash' tails, would share this
capability."
With one side-to-side flick, the researchers determined, a wave
of energy could accelerate through the length of one of the tapering,
segmented tails, gaining momentum to propel the tip of the tail to velocities
of more than
750 miles an hour, faster than the speed of sound.
"We must confess that it is pleasing to think that the first
residents of Earth to exceed the sound barrier were
not humans, but rather the diplodocid sauropods," Myhrvold and
Currie concluded.
Other dinosuar experts are sharply divided over the research.
Gregory S. Paul, an independent specialist in
dinosaur anatomy who is based in Baltimore, said he thought the
concept of sauropods with supersonic tails was
physically plausible. But at a recent paleontology conference, he
said, he heard "other people who just hate the
idea."
One critic is Dr. Kenneth Carpenter, a paleontologist at the
Denver Museum of Natural History. "To be blunt," he
said in an interview, "the computer simulations are another case
of garbage in, garbage out."
Carpenter questioned whether the bony segments of the dinosaur
tails could have produced a supersonice boom.
Even if that was possible, he said, using the tail like a whip
might have been both painful and damaging to
dinosaurs. The last few segments might even snap off.
In their report, Myhrvold and Currie emphasized that only the
last two or three inches of the dinosaur tail would
have exceeded the speed of sound. The possibility of pain or
damage might be minimized or eliminated, they
pointed out, if the most extreme part of the tail extended past
the last vertebra as a piece of skin, tendon, or
keratin, the protein that can take the form of scales, claws, or
feathers. "If whips made from the skins of cows
and kangaroos are able to withstand supersonic motion," they
said, "why not dinosaur skin and tendons?"
But the two researchers agreed with the paleontologists who now
reject the idea that the sauropods regularly
used their tails defensively. The animals would probably have
sustained as much injury to their tails as they
inflicted on attackers.
As chief technology officer at Microsoft, Myhrvold presumably has
more pressing research matters than dinosaur
tails. But dinosaurs have fascinated him since childhood, and he
has probably never met a research problem he
did not try to use a computer to solve. He got in the habit of
stretching the imagination when he studied
cosmology under Dr. Stephen W. Hawking at Cambridge University in
England.
"I don't claim it's relevant to Microsoft," he said of the
dinosaur simulations. "It's just an interesting problem to
me."
In particular, Myhrvold was intrigued by the analogy of the
bullwhip to explain the sauropod tails, as suggested a
few years ago by Dr. R. McNeill Alexander of the University of
Leeds, in England. The progressive rate of tapering
from the base of the tail to the tip is comparable to that of a
bullwhip from the grip to the tip. Each successive
vertebra in a sauropod tail is about 6 percent smaller than its
predecessor.
An analysis of fossils, especially those of an apatosaur at the
Carnegie Museum of Natural History, in Pittsburgh,
showed that in 41-foot tails of 80 vertebrae, the lengths of each
connecting segment reached a maximum of
some 4 inches in the section between the 18th and 25th vertebrae.
That happens to correspond to an area of
ossification, fusing pairs of vertebra and otherwise indicating
injuries from repeated stress.
As Myhrvold and Currie noted, the injury is consistent with
overextension of the tail joints from whiplike motions in
a plane parallel to the ground. Fossils suggest that the
sauropods could probably move their tails about 30
degrees side to side; for purposes of the computer simulations,
the researchers limited the motion to 9 degrees
side to side. The animals were presumably extremely limited in
vertical movements of their tails.
Next, Myhrvold recalled trying to learn everything possible about
whips. As a computer expert, he naturally consulted the Internet, but that
directed him mainly to discussions of sado-masochistic practices. Finally, he
learned that the man who made whips for Hollywood movies lived nearby in
Seattle. Purchasing one, after pledging to use it only for dinosaur studies,
he began to understand the Newtonian physics of whip dynamics, and he applied
this in adapting commercial software for conducting the computer simulations
of dinosaurian whiplike tails.
The two researchers offer several explanations for why sauropods
would have engaged in tail cracking. It might have been a way to enforce
discipline within a group, as herders of cattle and horses sometimes do with
whips. It might have been a way to resolve disputes without resorting to
combat. Or, they wrote, tail cracking "could have been used as a nonlethal
form of male-versus-male dominance contests."
What if the loud crack of a tail was a male's way of calling or
attracting females? A test of this idea, Myhrvold said, would be to study
many more fossils of dinosaur tails to see if the stress scarring was
confined to males. But paleontologists are not sure that they can
distinguish a male sauropod fossil from a female fossil.
Even if the issue of dinosaur tail cracking is never resolved,
Currie said, the computer simulations --cyberpaleontology -- promise to be
"the simple first steps for more complex models of dinosaur movements."